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15hp doesn't get past partial rpm

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pilot1950

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I'm working on a 9.9hp Evinrude for a friend, 1990 vintage I believe. Model plate is missing but very similar paint and decals as pictures identified as 1990. I didn't hear it run before he brought it over so was going just on his description of the symptoms. Sounded truly like a fuel starvation issue so I pursued that course. Replaced fuel pump, rebuilt carb (3 piece version with plastic top / bottom), checked spark with spark plug, checked compression (both roughly 120, not perfect) replaced fuel line from pump to carb and reassembled. Put it into a tank (garbage can) and it started on second pull. Will idle indefinitely and very nice. Took it to the lake for a power trial with my friend. This is the first I've heard it run above idle. Same symptom (he says) but to me, it sounds like just running on 1 cylinder. Now I'm no expert so could very well be wrong on that but it just wouldn't rev up. Brought it home and continuing the search. I've read lots of the comments from the smart people hear and really appreciate the advise given. I've read that the spark should jump a 7/16 gap and be quite blue. So I rigged up a test block to create gap and had the wife come watch for spark and color as I pulled the rope as briskly as I could. Sparked jumped the 7/16 gap on both coils but she says it's white. Is that of significance? This model has the CDI2 ignition which appears to have incorporated the power pack with the trigger under the flywheel? (just guessing here)

Suggestions on how to proceed. I had been told that power packs are either good or bad, work or don't work. Not get weak. I'll assume the charging coil is right next to it? The manual I have goes through 87 and doesn't cover the cdi2 ignition system so unsure how to check. I did check both coils and they appear to be good. Checked resistance on both the primary and secondary sides and were within spec. Friend had recently purchased a brand new fuel tank and hose, so I'm arbitrarily ruling that out. Plus, he says the symptoms didn't change with the new tank.

He had also installed new plugs. NGK BZ7HS - 10

I adjusted the timing (throttle roller / follower inline with the mark on the cam (just begin to open as it it centered on the roller). It was previously quite advanced. throttle didn't begin to open till well past the alignment mark.

There is no mechanical issue preventing full throttle.

Sorry for the rambling question, but wanted to make sure I included all that I did and all that I know about the motor and the history.

All comments and advise appreciated.

Added pics of what I believe is a 1990 model. Short shaft. Manual start.
 

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If ya think it is running on one jug...just run her enough to put some heat into it and feel both plugs, they should be equivalent in temp. An offending cylinder will be cool.

One can do all kinds of troubleshooting but this test is where to start.
 
Foolproof method.
when Its running, pull a spark plug wire. If nothing changes, it’s running on one- the other one.
of it dies, it was running in that one.
 
"I adjusted the timing (throttle roller / follower inline with the mark on the cam (just begin to open as it it centered on the roller). It was previously quite advanced. throttle didn't begin to open till well past the alignment mark."

How much advanced was it previously. Perhaps the previous owner had the same problem and adjusted this to accommodate it. Obviously you want your throttle adjusted correctly but perhaps it is directing you to where the problem might be. Does the carb roller look in good shape. Is it the right one.

As Edchris177 above indicated, first verify both cylinders are firing. His method is easy. Fire it up, warm it up, bring it to a fast idle and with an insulated pair of pliers, pull one spark plug boot at a time. If you pull a plug and the motor dies, then you know the other cylinder was not firing or is very weak.
 
Thank you gentlemen. I will definitely pursue the plug wire experiment. Glad to know I can do it a fast idle. I can do it at home in the big bucket. I'm going to guess that the previous timing setting was 1/8 to 3/16 past the roller centerline at throttle movement point. The roller seems to have lots of clearance on it's shaft (wobble) so when I set the timing I'm sure to take up all that clearance as well as other clearances in the linkage and look purely at throttle shaft movement for the adjustment.

While looking at the powerpack this morning (see picture above) I notice something that may be a concern. It appears to me as if there has been some mechanical interference between he pickup location on the powerpack and the inside magnets of the flywheel. Pictures included below.

It appears the charging coil outer radius should be set / located flush with the bosses on the ignition plate. How is the position of this powerpack established? There is some clearance in the mounting holes. I also noticed that there appeared to be loctite on the two screws for the charging coil and corrosion on the remaining screw for the powerpack. I'll clean all the corrosion before assembly. Wondering if all that was creating a weak ground for that system? Just wondering.

Addendum: Looking at my manual for the 87 model, there appears to be a special ring tool to fit over the armature plate bosses to align all these components. I don't have this tool but wonder if anyone would know the ID of that tool? 317001 Would be simple enough to make something to do that job.
 

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There are bevels on the bosses for the ignition and the coil. Push both back until they line up with the back edge of the bevel. Is your roller in one piece? They usually have a clear cover on them and they do fall off. Is the roller arm in good shape not broken?
 
Thanks. I'll look for those bevels. My roller is in one piece but it has no clear cover. I would describe it as a small thimble with a center hole. Smaller diameter main body with larger diameter "end caps". If it's supposed to be one common diameter, definitely the center is missing. Roller arm is not broken.

On a different note, my concern is growing for the obvious mechanical interference between the power pack and the flywheel ID (see pics above). don't know when that happened in the life of this engine, but it just doesn't seem like that's good. From what I read, the powerpack are a frequent failure item so must be delicate in several ways.
 
Is it a 15 or 9.9 HP ?-----This motor needs 4 things to run.------Correct amount of fuel.-----Spark at the right time.-----Compression in the cylinders.----And that elusive compression in each crankcase.----Some will argue , but I would look for a reed valve issue.
 
So sorry for the confusion. It's a 9.9. Can't figure out how to edit the thread title. Fairly certain that fuel isn't an issue. Spark at the right time? depends on condition of the powerpack. Compression? 120 in each cylinder. As for the crankcase compression, I'll have to learn more about that. You're suspecting one or more reed valves might be cracked or broken and therefore not sealing under compression?
 
I believe reed failures are rare but I agree it could cause the symptoms you are seeing. I remember there was a guy on one of these help sites who had a problem with his motor and later, after many agonizing hours of investigation, posted a picture of his reed valves. It had one of those plastic ties that are used to hold the fuel lines onto the carb or fuel pump, stuck in one of the reed valves, preventing it from closing. I guess someone took it off, lost it, and it must have got sucked through the carb throat into the intake manifold and lodged itself into the reed. Its inability to close and seal the crankcase would obviously affect the operation of one of the cylinders and would prevent the motor from reaching the higher RPMs.

Obviously you would want to do a cylinder drop test before you go to the trouble of investigating your reed valves. At least I would.
 
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pilot1950 said:
Thanks. I'll look for those bevels. My roller is in one piece but it has no clear cover. I would describe it as a small thimble with a center hole. Smaller diameter main body with larger diameter "end caps". If it's supposed to be one common diameter, definitely the center is missing. Roller arm is not broken.

On a different note, my concern is growing for the obvious mechanical interference between the power pack and the flywheel ID (see pics above). don't know when that happened in the life of this engine, but it just doesn't seem like that's good. From what I read, the powerpack are a frequent failure item so must be delicate in several ways.
Click to expand...
You need a new roller your center is missing. You are in gear revving this up correct? Does the gear safety move completely out of the way of the throttle. Does the carb open to 90 deg? Get rid of the NGK plugs and put the champions back in it. Is the inside of the flywheel look like it is rubbing?
 
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That was kind of why I asked about the roller upthread. I don't have that exact model so I could not say for sure but that roller looked kind of funny to me.
 
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